Percent change calculator
A→B change, reverse % change, and two-step changes

A → B

Percent change = (B − A) / |A| × 100%. If A = 0, percent change is undefined.

Fill inputs, then click Calculate.

Reverse (% → value)

New = Base × (1 + p/100). Negative p means decrease.

Fill inputs, then click Calculate.

Two-step % change

Overall multiplier = (1+p1/100)×(1+p2/100). Two changes don’t simply add.

Fill inputs, then click Calculate.
About / 關於

Percent change calculator — Compute percent change (A→B), reverse a percent change, and combine two-step percentage changes. Shareable, browser-only.

Example: Use this tool to sanity-check numbers quickly, then share the link if you need to discuss with others.

FAQ: (1) Does it upload my data? No—runs in your browser. (2) Can I share results? Yes—use the share link feature. (3) Is it authoritative? Treat it as a convenience, not professional advice.

漲跌幅（百分比變化）計算器 — 計算 A→B 漲跌幅、用 % 反推新值，並合併兩段 % 變化（避免直接相加的誤會）。可分享連結、純前端。

範例：用這個工具快速試算與對照結果，需要討論時再把連結分享給對方。

FAQ： (1) 會上傳資料嗎？不會，計算在瀏覽器內完成。 (2) 能分享結果嗎？可以，用分享連結。 (3) 準確嗎？請把它當作便利工具，不是專業建議。